linux-ext4 - Re: [PATCH] e2fsprogs: Don't report uninit extents past EOF invalid

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Date:	Mon, 12 Aug 2013 18:28:30 -0500
From:	Eric Sandeen <sandeen@...hat.com>
To:	Eric Whitney <enwlinux@...il.com>
CC:	linux-ext4@...r.kernel.org, tytso@....edu
Subject: Re: [PATCH] e2fsprogs: Don't report uninit extents past EOF invalid

On 8/12/13 6:21 PM, Eric Sandeen wrote:
> On 7/21/13 3:28 PM, Eric Whitney wrote:
>> Commit d3f32c2db8 caused e2fsck misbehavior during xfstests runs.
>> It reported that uninitialized extents created by fallocate() at
>> the end of file with the FALLOC_FL_KEEP_SIZE flag were invalid.
>> Because FALLOC_FL_KEEP_SIZE does not increase the file size when
>> an extent is fallocated, an uninitialized extent can legally contain
>> blocks past the end of file.
>>
>> The information reported by ext2fs_extent_get() and used by the commit
>> to determine legal extent ranges is limited by the value of i_size
>> (determines end_blk in the root extent index), so block values greater
>> than that containing i_size were reported as invalid.
>>
>> To fix this, filter out possible invalid extent candidates if they are
>> uninitialized and extend past the block containing the end of file.
>>
>> Signed-off-by: Eric Whitney <enwlinux@...il.com>
>> ---
>>  e2fsck/pass1.c      |    4 +++-
>>  lib/ext2fs/ext2fs.h |    1 +
>>  lib/ext2fs/extent.c |    1 +
>>  3 files changed, 5 insertions(+), 1 deletion(-)
>>
>> diff --git a/e2fsck/pass1.c b/e2fsck/pass1.c
>> index ba6025b..b84b0d0 100644
>> --- a/e2fsck/pass1.c
>> +++ b/e2fsck/pass1.c
>> @@ -1892,7 +1892,9 @@ static void scan_extent_node(e2fsck_t ctx, struct problem_context *pctx,
>>  			problem = PR_1_EXTENT_BAD_START_BLK;
>>  		else if (extent.e_lblk < start_block)
>>  			problem = PR_1_OUT_OF_ORDER_EXTENTS;
>> -		else if (end_block && last_lblk > end_block)
>> +		else if ((end_block && last_lblk > end_block) &&
>> +			 (!(extent.e_flags & EXT2_EXTENT_FLAGS_UNINIT &&
>> +			    last_lblk > info.eof_blk - 1)))
>>  			problem = PR_1_EXTENT_END_OUT_OF_BOUNDS;
>>  		else if (is_leaf && extent.e_len == 0)
>>  			problem = PR_1_EXTENT_LENGTH_ZERO;
>> diff --git a/lib/ext2fs/ext2fs.h b/lib/ext2fs/ext2fs.h
>> index 311ceda..85f2ac8 100644
>> --- a/lib/ext2fs/ext2fs.h
>> +++ b/lib/ext2fs/ext2fs.h
>> @@ -409,6 +409,7 @@ struct ext2_extent_info {
>>  	int		bytes_avail;
>>  	blk64_t		max_lblk;
>>  	blk64_t		max_pblk;
>> +	blk64_t         eof_blk;
>>  	__u32		max_len;
>>  	__u32		max_uninit_len;
>>  };
> 
> I just realized, this affects the ABI, doesn't it?  Hm.
> 
> As a hack-around, can probably just use ehandle->path[0].end_blk directly
> in scan_extent_node and stash eof_blk locally?

Nope, we can't crack an extent handle, it's an opaque type.

Ned some V2 interfaces now?  :(

> -Eric
> 
>> diff --git a/lib/ext2fs/extent.c b/lib/ext2fs/extent.c
>> index 65bb099..de54319 100644
>> --- a/lib/ext2fs/extent.c
>> +++ b/lib/ext2fs/extent.c
>> @@ -1572,6 +1572,7 @@ errcode_t ext2fs_extent_get_info(ext2_extent_handle_t handle,
>>  	info->max_depth = handle->max_depth;
>>  	info->max_lblk = ((__u64) 1 << 32) - 1;
>>  	info->max_pblk = ((__u64) 1 << 48) - 1;
>> +	info->eof_blk = handle->path[0].end_blk;
>>  	info->max_len = (1UL << 15);
>>  	info->max_uninit_len = (1UL << 15) - 1;
>>  
>>
> 
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